The research includes the following: (1) studies of the chemical modification of allosteric sites of rabbit muscle phosphofructokinase (PFK), including and examination of the kinetic properties of PFK modified at the AMP binding site and of PFK hybrids containing native enzyme and enzyme with either a modified reactive thiol group, a modified citrate site, a modified ATP inhibitory site, or a modified AMP site; (2) a study of the characterization, distribution, and physiological role of multiple enzymic forms of PFK with particular emphasis on the yet to be characterized C isozyme; (3) and a study of the structural and regulatory significance of phospho- and dephospho- forms of muscle PFK. Immediate goals for this project are: 1) determine differences in activity and/or stability in phosphorylated and non-phosphorylated enzyme. 2) extend studies of the possible differences in phosphorylation state of muscle PFK in normal and diabetic mice. 3) characterize more completely the C isozyme of brain and determine the role of phosphorylation in this enzyme.